Commonwealth to scrap royal succession rules

Commonwealth nations have agreed to scrap centuries-old laws barring first-born daughters or anyone married to a Roman Catholic from inheriting the British throne.

British prime minister David Cameron said the agreement, unanimously backed by all 16 nations where Queen Elizabeth II is head of state, represented an "historic moment" for the monarchy.

He said the changes, which will have to be formally approved by the affected nations, would sweep aside "outdated rules [that] just don't make sense to us any more".

"We will end the male primogeniture rule so that in future the order of succession should be determined simply by the order of birth," Mr Cameron told reporters at the CHOGM gathering in Perth.

"We have agreed to scrap the rule which says that no one that marries a Roman Catholic can become monarch," he added.

Mr Cameron has the political support to make the changes in Britain but needed approval from the 15 other Commonwealth realms, including Canada, Australia, New Zealand and smaller nations in the Caribbean and the Pacific.

The British leader said there had been talk about changing the succession rules for some time but organising reform across so many countries was a complex issue.

The succession debate intensified with the wedding in April of Prince William, the second in line to the throne, and Kate Middleton.

"Put simply, if the Duke and Duchess of Cambridge were to have a little girl, that girl would one day be our queen," Mr Cameron said, referring to the royal couple's official titles.

He said the monarch would still have to be Protestant because he or she heads the Church of England.

The law also formalised the policy of male primogeniture, although the tradition dates back even further to feudal times and beyond.

Under the law, female heirs to the throne are passed over if younger male heirs are available. Queen Elizabeth II was crowned in 1953 only because she did not have any brothers.

There has been a reluctance to press the issue in the past, partly due to concern that tinkering with the rules may encourage republican movements in countries such as Australia.

However, the monarchy has enjoyed a surge in popularity in the wake of William and Kate's marriage, with adoring crowds greeting the Queen on her current tour of Australia.

Prime Minister Julia Gillard said there was far less focus in Australia on cutting ties with the monarchy than before a failed republic referendum in 1999.

"Ultimately I think the Australian people will work their way through changes to our constitutional arrangements but there is a not a great deal of focus on this in our current national discourse," she said.

"The Queen has certainly been received with a great degree of affection on this visit."

Ms Gillard welcomed the proposed succession changes as "simple and very rational" but noted they would alter forever the way the monarchy works.